Well I know for the catted X pipe and the Catback together it is 19rwhp and 17rwtq........
I believe the catback by itself was around 10rwhp.....
not quite the same gains as the 99-04s, but we attribute much of that to the fact that they are coming with 2.5" from the factory now-
(99-04s have consistenly shown 12-14rwhp gains with just a cat back)
We experimented with some other pipe sizes- 2 3/4, 3" as well, and we were not happy with the dyno results as they seemed to loose a lot of mid range power with the bigger pipe diameters.
Of course Cobras don't respond that well to pipe bigger then 2.5, unless extremely modified, so we didnt think this car would either......